Synthesis and investigation on liquid crystal and optical properties of dyads based on triphenylene and perylene

Abstract

Four novel mesogenic dyads consisting of a hexa(alkoxy)triphenylene donor that was linked to a perylene tetracarboxylic esters acceptor by the bridges (O–(CH₂)₂–O), (O–(CH₂)₆–O), (O–(CH₂)₁₀–O) and (O–(CH₂)₁₂–O), had been synthesized. Their structures were characterized by ¹³C and ¹H nuclear magnetic resonance (NMR), infrared spectroscopy (IR) and elemental analysis (EA). The experimental results of cyclic voltammetry and UV/Vis showed the aliphatic linkage of the donor–acceptor dyads preserved the genuine electrochemical behaviors and light absorption properties of the donor and acceptor units, and the energy level difference between the HOMO of the donor and the LUMO of the acceptor is about 1.94 eV. The differential scanning calorimetry (DSC) traces and polarizing optical microscopy (POM) textures confirmed that all dyads had mesophase. When excited at 443 nm, fluorescence quenching process of the acceptor unit was ascribed to a intramolecular ground-state charge transfer from the donor to it. And the fluorescence quenching varying with the bridge lengths were understood by Dexter-type energy transfer theory. These behaviors of photoinduced intramolecular charge transfer and forming columnar liquid crystal phase made these dyads candidates of new active materials in organic solar cells.